When washing or cleaning articles, such as garments, consumers prefer that such articles maintain their colour, even after repeated cleaning cycles. This is especially true with white materials, as their colour is closely associated with cleanliness. However, the perception of colour, and in particular whiteness, varies between consumers. The variations in perception are believed to be the result of a number of cultural and social factors, including the cultural colour associations of the observer. For example, Egyptian and Mexican consumers typically perceive a blue hue as white, while Indian consumers typically perceive a violet-pinkish hue as white.
While some dyes, when used in a cleaning or treatment composition, may improve the whiteness perception of a material, they can build-up or deposit unevenly on the material, which may lead to discoloration and spotting. In such cases the whiteness perception may in fact be decreased or, at worst, spotting may be seen. This is particularly the case when higher concentrations of such dyes are used under stressed conditions, such as long soak times and/or cold water conditions. While several techniques have been used to increase the efficiency of deposition on materials (See for example WO 2000/18862, WO 99/14245, WO 98/29528, WO 98/00500, WO 95/30042, U.S. Pat. Nos. 6,579,842, 6,586,384, 5,972,049, and 3,597,304) there remains a need for cleaning and/or treatment compositions that can provide tailored colour perceptions, such as whiteness or blackness without dye build-up or spotting.
Another problem associated with the use of such dyes in heavy duty liquids is that the dye will dominate the colour of the liquid detergent itself, limiting the range of colours achievable for detergents comprising the dye. Consumers will often choose a product depending on its colour and so there is a need to be able to provide detergents of different colours, but which also comprise a dye which imparts the correct tailored colour perception for that particular consumer group.
The present invention seeks to provide an improved liquid detergent composition for providing tailored colour perception.